In the fields of microbiology, fermentation etc. it is frequently necessary to screen microbial cultures to distinguish between cells with different attributes or identify cells with similar attributes, for example viable and non-viable cells, or the level of productivity of a useful metabolite. One field in which such screening is particularly useful is in biotechnology, where microbial line development involving mutation of cells by mutagenic radiation or chemicals is carried out. After a microbial culture has been exposed to mutagenic influences it is necessary for the culture to be screened to detect mutations of interest. As the ratio of useful mutations to useless mutations is usually very low and the number of cells to be screened is usually very large it is desirable that fast and effective, ideally automated, processes are provided to carry out as much as possible of the screening.
Automated cell screening apparatus are known, but at present these can only screen relatively small numbers of cultures per year, and there is a need to improve on the rate of screening.